(1) Field of the Invention:
The present invention relates to a novel solid lubricant-containing collector having an excellent abrasion resistance and to a process for the preparation of this novel collector.
(2) Description of the Prior Art:
In general, collectors used for electric trains, cranes, hoists or the like are composed of copper type sintered alloys, lead impregnated iron type sintered alloys or aluminum type sintered alloys. Each of these collector materials, however, is defective in that since the material is inferior in its electric conductivity, thermal conductivity, abrasion resistance and strength, consequently the life of the collector is very short. The reason for these defects is that since a solid lubricant is uniformly dispersed by sintering in production of each of the foregoing collector materials, a great number of voids are present in the alloy structure and sintering cannot be performed completely until a theoretical density is attained. If the electric conductivity is low, a sufficient electricity collecting efficiency cannot be obtained. If the thermal conductivity is low, the material is heated by the resistance during the electricity-collecting operation and since the heat discharge rate is low, the temperature is further elevated and the collecting efficiency is lowered. If the abrasion resistance and the strength are low, in case of a collector of an electric train for collecting electricity from an aerial line in sliding contact therewith, the collector is readily worn by sliding and its life is very short. Furthermore, a collector of a material having a low strength involves a danger that it will be broken under a pressing force.
As will be apparent from the foregoing illustration, a collector material is required to have high electric conductivity, high thermal conductivity, excellent abrasion resistance and high strength. The life of a collector depends greatly on the abrasion resistance of a collector material, and a material having a high abrasion resistance is especially required for production of a collector.
It is also required of a collector that the phenomenon of "separation from a line" should be reduced. By this "line separation" phenomenon is meant a phenomenon in which a collector for collecting electricity while sliding, such as a pantograph, separates from an aerial line during running and electricity is not collected. The line separation ratio is expressed in terms of the ratio of the line separation distance to the running distance. Accordingly, it is required that the collector should have a low line separation ratio. This line separation ratio is varied dependent on the weight of the collector and the thickness of the oxide film. As the weight of the collector is heavy, the line separation ratio is increased. An arc discharge is caused by the line separation, damaging the aerial line or collector, and further, the running speed is reduced. In order to reduce the line separation ratio, it is necessary to lower the running speed of the train or to increase the tension of the aerial line or the pressing force of the pantograph. Reduction of the running speed is contradictory to the desirable high speed operation and increase of the pressing force is not preferred because abrasion damages of the aerial line or collector are made serious. In other words, use of a heavy collector results in increase of the pressing force and abrasion damages. In conclusion, in order to reduce the line separation ratio, it is necessary to lighten the weight of a collector. Namely, reduction of the line separation ratio can be attained by the use of a collector material having a low specific gravity or being excellent in strength, abrasion resistance and electric conductivity.